Vascular changes, a common finding longstanding diabetes, can severely impair physiological functions in many different parts of the body. Once formed, vascular lesions are largely irreversible. Changes in retinal vessels can result ultimately in blindness. Rigid control of blood sugar is thought to diminish vascular changes, but most diabetics cannot maintain such tight control over a period of years. Until the biochemical basis of diabetic vascular changes is understood, therapeutic possibilities other than rigid control will be limited. Within the last decade, significant progress has been made in understanding the nature of vascular basement membranes. This knowledge permits a closer look at the effect of diabetes on these basement membranes. The overall objective of this project is to obtain basic informationon the effect of diabetes on basement membranes. The specific aims are to determine the effect of diabetes on the composition and subunit structure of ocular and brain basement membranes, to assess the role of nonerzymatic glycosylation on crosslink formation in basement membranes, to identify the mechanism of basement membrane thickening frequently observed in longstanding diabetes, to determine the nature of membranes synthesized by retinal capillary endothelial and epithelial cells in culture, and to determine the effect of several parameters characteristic of the diabetic state on cell growth and the biosynthesis of these membranes. Compositional studies will involve amino acid, carbohydrate, and hydroxylysine glycoside analyses. Representative samples will be examined by electron microscopy so that valid compositional comparisons can be made. Subunit structural studies will entail solubilization of basement membranes, separation of the subunits on the basis of size and charge, and characterization of the various subunits. The assessment of nonezymatic glycosylation on crosslink formation will be performed on lens capsules obtained from whole lens cultures. The mechanisms of basement membrane thickening will be determined in retinal and brain vascular basement membranes after labelling with silver. Membrane biosynthesis and the effect of several parameters characteristic of the diabetic state on cell growth and membrane biosynthesis will be performed using retinal capillary pericytes and endothelial cells grown in culture.